Field of the Invention
The present invention relates to a high strength Ni—Cr—Mo—W—Nb—Ti welding filler metal and weld deposit and a method of creating a weld deposit using the welding filler metal and, more particularly, to a Ni—Cr—Mo—W—Nb—Ti welding filler metal used to produce a weld deposit having high yield strength in the as-welded condition.
Description of Related Art
During off-shore exploration, development, and production of crude petroleum, there is a need for laying pipe at a rapid rate in order to minimize the time of employment of very expensive “lay barges”. This need is met by the concept of “Reeling” long lengths of ID clad pipe welded end-to-end on dry land at facilities called “Spool Bases”. These facilities are quite expensive to operate and have multiple stations within the base for preparation, welding, serially sequenced NDE inspection, and coating of long lengths of high-strength ID-clad X-65, X-70, and X-80 pipe. While at sea, joining ends of reels is even more time-sensitive than that required at Spool Bases due to the elevated cost of lay-barge operations. Spool Base operators and lay-barge welders are reluctant to use precipitation-hardened weld metals such as INCO-WELD Filler Metal 725NDUR that require elevated temperature hold times to develop high strength via precipitation hardening because it would slow the process and perhaps have a negative effect on the high strength steel pipes.
Due to the desire to operate these “Spool Bases” most efficiently, gas metal arc welding (GMAW) is used because of the faster rate of welding.
Thus, there is a need for a welding wire that may be used with the gas metal arc welding process that exhibits the same or slightly better corrosion resistance in sour oil and gas applications than the INCONEL® alloy 625 (58.0% min. Ni, 20.0-23.0% Cr, 5.0% max. Fe, 8.0-10.0% Mo, 3.15-4.15% Nb, 0.10% max. C, 0.50% max. Mn, 0.50% max. Si, 0.015% max. P, 0.015% max. S, 0.40% max. Al, 0.40% max. Ti, and 1.0% max. Co, in weight %). This wire is needed to weld ID-clad high-strength pipes made of American Petroleum Industry Specification 5L (API 5L) X-65, X-70, and X-80 steels while providing greater yield strengths in the as-welded condition than each of the base steels being welded. The desirable weld metal would have a yield strength that is approximately 14.5 ksi (100 MPa) greater than the minimum yield strength specified for the pipe that is being welded since qualifications require that transverse two-thickness (2T) 180 degree bends must be performed on the actual pipe being used, and transverse tensile tests must fail in the base metal. Additionally, an overmatch in strength would be desirable to facilitate “Reeling” without the possibility of kinking at or near the welds.